Inertia switch having releasable latch means

ABSTRACT

The invention provides an inertia switching device defining a seating, an operating mass of magnetic material normally retained in the seating by means of a magnet positioned adjacent the seating and an actuating member slidably mounted within the housing and displaceable from a first to a second position by the magnetic-operating mass upon dislodgement thereof from the seating upon application of an external perturbation to make or break an electrical circuit, and means mounted on or adjacent the actuating member and coacting with the housing to maintain said member in its second position.

United States Patent nu 3,569,643

[72] Inventors Walter Wilson Hugh Clarke; [56] References Cited Terence Alexander Riley, Surrey, England UNITED STATES PATENTS pp 854,377 3,493,701 2/1970 Clarke ZOO/61.45 221 Filed Sept. 2, 1969 I 5 patented Man 9, 1971 Primary Examiner-Robert S. Macon 731 Assignee C.B. Associates Limited Assistant Examiner-M Gmsburg L England Attorney-Woodhams, Blanchard and Flynn [32] Priority Sept. 3, 1968, Nov. 19, 1968 E 919/68 ABSTRACT: The invention provides an inertia switching [54] INERTIA SWITCH HAVING RELEASABLE LATCH MEANS 10 Claims, 3 Drawing Figs. [52] U.S. Cl ZOO/61.53 s 1 1111. c1 g non; as /14 [50] Field of Search ZOO/61.45, 61 .5 3

device defining a seating, an operating mass of magnetic material normally retained in the seating by means of amagnet positioned adjacent the seating and anactuating member slidably mounted within the housing and displaceable from a first to a second position by the magnetic-operating mass upon dislodgement thereof from the seating upon application of an external perturbation to make or break an electrical circuit, and means mounted on or adjacent the actuating member and coacting with the housing to maintain said member in its second position.

PATENTED "AR 9 I9?! l/VVENIUAS WHITE)? WILSON HUGH CLHRKE BifKENCE ALEXANDER RILEY mmmnmwim AITOR/VEYS BNERTIA SWITCH HAVING RELEASABLE LATCH MEANS The invention relates to inertia switches, that is to say, switches operated by movement of the switch as a whole, for example by tilting, impact vibration, acceleration, retardation, or any other external perturbation.

Such inertia switches are applicable for electrical and fluid circuits.

Known inertia switches are costly to manufacture and in consequence have not been widely used in domestic appliances, since their provision would necessitate a disproportionate increase in the retail price of the appliance. Such switches have many uses, for example to cut out the supply of electricity to a drive motor when a washing machine or spin drier exceeds a determined amplitudeof oscillation due to overor eccentric-loading of the drum. Another use is to disconnect the electrical system of a vehicle, for example in the event of a crash.

It is among the objects of the invention to provide a simple and inexpensive switching device including a housing, an elongated actuating member, an inertia mass and a releasable latching means.

It is also among the objects of the invention to provide a simple inertia switch that is operative on the action of an external perturbation.

According to the invention, furthermore, the operating mass may be a sphere, the seating may be frustoconical, and

the magnet may be mounted near the apex of the seating.

According to the invention still further, the releasable means may comprise a latch member.

Advantageously the slidable member is T-shaped, each arm of which rests on a contact when the switch is at rest.

The arms of the T-shaped member may, however, be adapted to contact the contacts when the switch is actuated under perturbating force, the circuit 'then being made from one terminal, through the member to the other terminal.

Alternatively, the elongated member may be a cylindrical shank. The shank may preferably include a peripheral groove such that on displacement of the members by the operating mass the groove is brought adjacent at least one of the contacts thereby to isolate the contacts.

At the same time a spring biased plunger mounted in the wall of the housing enters the groove to retain the member in its displaced position. Alternatively the groove shank may complete an electrical contact through the contacts when displaced.

The operating mass may be provided in other than a spherical form, for example as a cylinder located in a recessed seating of part circular configuration in cross section. In this case the switch will only respond to an acceleration in the direction of its axis. Furthermore, by small modifications of the switch additional contacts may be operated if required.

The invention is illustrated, by way of example only, in the accompanying diagrammatic drawings, in which:

FIG. 1 is a top plan view of a one embodiment of an inertia switch;

FIG. 2 is a longitudinal sectional view of the switch shown in FIG. l; and v FIG. 3 shows a longitudinal section through a second embodiment of the inertia switch.

The switch shown in FIGS. 1 and 2 comprises a housing formed as a cup I and a seating assembly 2 engaged therewith formed by injection moulding from a plastics material. A magnet 3 is secured in a bore of the seating assembly 2. A ball 5 of magnetic material is held on the frustoconical seating by the attraction of the magnet. An elongated T-shaped slidable actuating member 6 is provided above the ball, the arms of the T-shaped member resting on terminals 8,8. The cup I is secured to a top part of the housing-by screws, bolts or welding, the part 10 having a central bore coaxial with the member 6 and in which slides a locking member 9 formed as a latch spring. The latch spring 9 is secured to the member 6, as

for example by screws. A load spring 7 surrounding the latch spring 9 extends between the flat, upper surface of the T- shaped member 6 and an inner surface of the housing part 10 which forms an abutment for an upper part of the spring 7.

In operation, upon vibration or acceleration of the switch in a plane at right angles to its longitudinal axis, the ball 5 is shaken loose from its seating and overcomes the attraction of the magnet 5. The ball 5 rises upwardly to strike the member 6, which is lifted clear of the terminals 8, thereby breaking the circuit, against the pressure of the load spring. The latch spring 9 is also raised by this action. When the latch parts or shoulder portions of the spring 9 emerge from the bore 11, the latch spring 9 expands laterally and 'the latch spring is effective to support the member 6 clear of the terminals.

To reset the switch, the latch parts of spring 9 are pinched together and the latch spring 9 is pushed downwardly into the bore 11 until the member 6 again rests on the terminals 8. The ball 5 is pushed back into its seating by this action, or the ball returns to its seating when acceleration of the switch ceases.

It is to be understood that the member 6 may close a circuit when it is struck by the ball. In this embodiment, the terminals 8 are situated above the member 6. In both embodiments the body part of the member 6 depending towards the ball passes through an internal bore in the casing, which bore is effective to maintain the member 6 centrally within the switch.

The switch shown in FIG. 3 comprises a two-part housing 12 secured together by means of screws or screw threads, for example. The housing defines an internal cavity containing a ball or sphere 13 of magnetic material which sits normally upon a frustoconical seat 14 under the influence of a magnet 15. The upper part of the housing contains a slidable cylindrical member 16 having a shoulder at the top to limit the travel. The lower end of a cylindrical shank I7 of the member 16 protrudes into the cavity. A pair of contact terminals 18 are embedded in or otherwise secured to the upper part of the housing and terminate inwardly in contact with the shank 17 of the member 16. Only one terminal 18 is shown in the FIG., the other being offset circumferentially therefrom. The upper part of the housing is formed with a transverse bore which contains a plunger 19 urged by a spring 20 into engagement with the shank. The plunger and spring are retained within the bore by a cap 21 which is threaded into the bore. Alternatively the plunger 19 may be replaced by a ball. Preferably the two contacts and the plunger or ball are offset circumferentially at substantially with respect to one another.

The shank 17 is fon'ned with a peripheral groove 22.

When the switch isactuated and member 16 is lifted by the sphere 13, the plunger 19 enters the groove 22 to retain the member 16 in a position to break the circuit between the contacts 18. At this position the contact 18 shown is isolated from the shank by virtue of the peripheral groove. To reset the switch, the upper end of the member 16 is pushed down to the position shown in the FIG. It will be appreciated that the housing is formed from a nonconducting material such as a synthetic plastics material. The shank portion of the member 16 may be formed from an electrical conducting material or from insulating material and carry an annular collar 23 which is made of conducting material in the region of the contacts 18.

The embodiment illustrated is a switch which when actuated breaks a circuit between electrical contacts. The switch can readily be modified to complete a circuit between two normally isolated contacts. That is, the groove 22 would be radially aligned with the contacts 18 when the member 16 is in its normal position shown in FIG. 3;

It is also to be understood that in every embodiment the magnet may be fixed or alternatively adjusted in position relative to the seating to provide varying attractive forces towards the ball or sphere.

The magnet may also be cylindrical, of square cross section or U-shaped, or of any other suitable shape.

We claim:

ll. An inertia switch device, comprising:

housing means having a seat formed thereon;

magnet means mounted on said housing means and positioned adjacent said seat;

an actuating member movably mounted on said housing means for movement between first and second positions, said actuating member having a portion disposed opposite said seat with said actuating member being normally maintained in said first position, movement of said actuating member to said second position causing said portion to be moved away from said seat;

electrical contacts fixedly mounted on said housing means coacting with said actuating member for creating an electrical circuit when said actuating member is in one of said positions; an inertia mass movably disposed within said housing means between said seat and said portion of said actuating member, said inertia mass being normally magnetically attracted to said magnet means so as to be held in engagement with said seat whereby imposition of a shock force on said switch device causes said inertia mass to be moved away from said seat so as to strike said portion of said actuating member and move said actuating member from said first position to said second position; and

releasable latch means separate from said electrical contacts acting between said actuating member and said housing means when said actuating member has been moved to said second position for holding said actuating member in said second position.

2. A switch device according to claim 1, wherein said actuating member is of T-shaped configuration in side elevation, and has conductive arm means engageable with said contacts, said releasable latch means including a spring latch secured to said actuating member, said spring latch having a shoulder portion urged out of said housing means for engaging a part of same for resiliently holding said actuating member in said second position.

3. A switch device according to claim 2, wherein said actuating member is normally urged into said first position by a spring mounted encircling said spring latch between said actuating member and an abutment on said housing means.

4. A switch device according to claim 2, wherein said arm means of said actuating member contacts said electrical contacts in said first position to make an electrical circuit.

5. A switch device according to claim 1, wherein said actuating member includes an elongated shank having a peripheral groove and said releasable latch means includes a plunger mounted in a bore of said housing means, and spring means urging one end of said plunger into said groove when said actuating member is in said second position, and means holding the other end of said plunger against movement relative to said housing means.

6. A switch device according to claim 5, wherein there are a pair of said electrical contacts, said pair of electrical contacts and said plunger being mounted in said housing means and mutually displaced circumferentially.

7. A switch device according to claim 1, wherein said magnet means is cylindrical.

8. A switch device according to claim 1, wherein said magnet means is square in cross section.

9. A switch device according to claim 1, wherein said magnet means is fixedly mounted in said housing.

10. A switch device according to claim 1, wherein said magnet means is mounted for adjustment in position in said housing. 

1. An inertia switch device, comprising: housing means having a seat formed thereon; magnet means mounted on said housing means and positioned adjacent said seat; an actuating member movably mounted on said housing means for movement between first and second positions, said actuating member having a portion disposed opposite said seat with said actuating member being normally maintained in said first position, movement of said actuating member to said second position causing said portion to be moved away from said seat; electrical contacts fixedly mounted on said housing means coacting with said actuating member for creating an electrical circuit when said actuating member is in one of said positions; an inertia mass movably disposed within said housing means between said seat and said portion of said actuating member, said inertia mass being normally magnetically attracted to said magnet means so as to be held in engagement with said seat whereby imposition of a shock force on said switch device causes said inertia mass to be moved away from said seat so as to strike said portion of said actuating member and move said actuating member from said first position to said second position; and releasable latch means separate from said electrical contacts acting between said actuating member and said housing means when said actuating member has been moved to said second position for holding said actuating member in said second position.
 2. A switch device according to claim 1, wherein said actuating member is of T-shaped configuration in side elevation, and has conductive arm means engageable with said contacts, said releasable latch means including a spring latch secured to said actuating member, said spring latch having a shoulder portion urged out of said housing means for engaging a part of same for resiliently holding said actuating member in said second position.
 3. A switch device according to claim 2, wherein said actuating member is normally urged into said first position by a spring mounted encircling said spring latch between said actuating member and an abutment on said housing means.
 4. A switch device according to claim 2, wherein said arm means of said actuating member contacts said electrical contacts in said first position to make an electrical circuit.
 5. A switch device according to claim 1, wherein said actuating member includes an elongated shank having a peripheral groove and said releasable latch means includes a plunger mounted in a bore of said housing means, and spring means urging one end of said plunger into said groove when said actuating member is in said second position, and means holding the other end of said plunger against movement relative to said housing means.
 6. A switch device accordIng to claim 5, wherein there are a pair of said electrical contacts, said pair of electrical contacts and said plunger being mounted in said housing means and mutually displaced circumferentially.
 7. A switch device according to claim 1, wherein said magnet means is cylindrical.
 8. A switch device according to claim 1, wherein said magnet means is square in cross section.
 9. A switch device according to claim 1, wherein said magnet means is fixedly mounted in said housing.
 10. A switch device according to claim 1, wherein said magnet means is mounted for adjustment in position in said housing. 